Genetics

Question 1

in brittle bones what does the sequence change cause

Answer 1

sequence changes from GGC to TGC causing glycine to become cysteine. cysteine can form disulphide bridges linking two chains.

Question 2

what breaks the bridges formed in brittle bones

Answer 2

2-mercaptoethanol

Question 3

why are only some alpha collagen chains affected

Answer 3

have two copies of Co1A! gene so only some collagen carries the mutation, need two copies of the mutated protein to combine

Question 4

how does the change from gylcine to cysteine alter the structure

Answer 4

glycine is small and can be in the centre of the triple helix, other amino acids wont fit, will make unstable

Question 5

what type of mutation is brittle bones

Answer 5

gain of function mutation

Question 6

why would changes cause bone abnormalities

Answer 6

skeleton laid down as collagen and mineralised later, if collagen is defective then bones are

Question 7

prenatal diagnosis for brittle bone disease

Answer 7

Restriction fragment length polymorphism
mutation removes or makes restriction site, DNA digested, Gel electrophoresis using a probe region of dna near mutation.
PCR to amplify region with mutation then gel electrophoresis and probe for mutation